Re: writeback hang in current mainline

[Jens Axboe <jens.axboe@oracle.com>]

On Wed, May 26 2010, Jens Axboe wrote:
> On Wed, May 26 2010, Christoph Hellwig wrote:
> > On Wed, May 26, 2010 at 02:56:15PM +0200, Jens Axboe wrote:
> > > On Wed, May 26 2010, Christoph Hellwig wrote:
> > > > On Wed, May 26, 2010 at 02:21:26PM +0200, Jens Axboe wrote:
> > > > > Ugh ok I see it, I had the caller_frees reverted. Try this :-)
> > > > 
> > > > This seems to fix it.  Running some more tests now.
> > > 
> > > Goodie, then the analysis at least is correct. A potentially cleaner fix
> > > would be to just allocate the WB_SYNC_NONE && sb_pinned work struct on
> > > the stack, since then we can get rid of that nastiness in
> > > wb_work_complete() as well (and not pass 'sb_pinned' around so much).
> > > 
> > > If you have time, care to test this one as well?
> > 
> > Both this and the previous one hang hard in xfstests 007, with no chance
> > of getting a backtrace.
> > 
> > For now I would recommend to revert
> > 21c12849fef73efc9a898b6702fe421fd774f515 and
> > 29c795f02e68ecd7bb1374844d3e55e882ac158f,
> > which makes xfstests run fine for me.
> 
> OK, thanks for the testing. I'll revert the two and work up a real
> solution once I have the test equipment online again.

BTW, if you have one more chance to test... Use the latest one, but also
apply this one:

http://lkml.org/lkml/2010/5/26/215

which fixes a silly thinko that's closely related to this logic.

-- 
Jens Axboe

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